The present invention relates to an image forming apparatus and a fixing temperature control method therefor.
In an image forming apparatus, to start a print operation without taking a long resumption time at the time of copy, control is performed to make a fixer hold a predetermined fixing temperature (e.g., 200° C.) in a normal standby state.
In a conventional image forming apparatus disclosed in patent reference 1 (to be described later), in the standby state, when the approach of an operator to the apparatus is detected in accordance with, e.g., the open/close operation of the document feed table, the temperature of the fixer is raised from the temperature in the standby state to a temperature necessary for fixing processing.
In an image forming apparatus disclosed in patent reference 2 (to be described later), when an original is placed on the original table, and the operation of the operation unit is started, the temperature of the fixer is raised from the temperature in a sleep state or preheat state to a temperature necessary for fixing.
In an image forming apparatus described in patent reference 3 (to be described later), when an enormous number of copies are to be made by using paper sheets with a large size such as A3, the standby temperature of the fixer is raised before the start of copy. After the temperature has risen, copy is started.
In these conventional image forming apparatuses, the fixer in the standby state must be held at a predetermined temperature.
However, if control is executed to always maintain the fixer temperature at, e.g., 200° C., in the standby state, power is wasted while the apparatus is not used.
To prevent such wasteful power consumption, when the user does not use the apparatus for a predetermined time, a power saving operation starts to decrease the fixer temperature to about 100° C.
However, control is performed such that the normal fixer temperature (e.g., 200° C.) is maintained for a predetermined period, i.e., during the period until the apparatus shifts from the standby state to the power saving operation. Hence, power consumption during this time cannot be reduced.
If the fixer temperature during this time is reduced, and the user wants to start copying, the time (first copy time) necessary for the first copy may be long.
Alternatively, assume that a continuous copy operation is to be executed, and particularly, the heat capacity of the fixer is low. Since the fixer is left to stand for a long time in a low temperature state, paper sheets absorb heat in printing, and the heat amount of the fixer decreases. Accordingly, the fixer temperature decreases. As a result, the standby operation may start again during the copy operation to interrupt it or cause fixing errors.
References that disclose the conventional image forming apparatuses are as follows.
Patent reference 1: Japanese Patent Laid-Open No. 06-324531
Patent reference 2: Japanese Patent Laid-Open No. 03-279966
Patent reference 3: Japanese Patent Laid-Open No. 11-327356
As described above, in the conventional image forming apparatuses, if power consumption in the standby state is to be reduced, long time is required until the temperature rises to the fixing temperature necessary for the actual start of printing. This may result in a decrease in operability, productivity, and copy quality.
The present invention has been made in consideration of the above situation, and has as its object to provide an image forming apparatus capable of reducing power consumption without any decrease in operability, productivity, and copy quality, and a fixing temperature control method therefor.